U.S. patent application number 11/309569 was filed with the patent office on 2007-11-01 for heat pipe with non-metallic type wick structure.
This patent application is currently assigned to FOXCONN TECHNOLOGY CO., LTD.. Invention is credited to CHUEN-SHU HOU, TAY-JIAN LIU, CHAO-NIEN TUNG.
Application Number | 20070251673 11/309569 |
Document ID | / |
Family ID | 38647238 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070251673 |
Kind Code |
A1 |
HOU; CHUEN-SHU ; et
al. |
November 1, 2007 |
HEAT PIPE WITH NON-METALLIC TYPE WICK STRUCTURE
Abstract
A heat pipe includes a casing (100) and a capillary wick (200)
received in the casing. The casing has an evaporating section
(400), a condensing section (600) and a central section (500)
between the evaporating section and the condensing section. The
capillary wick arranged at the central section is made of
non-metallic material. The capillary wick at the central section of
the casing provides a low cost and a lightweight to the heat
pipe.
Inventors: |
HOU; CHUEN-SHU; (Tu-Cheng,
TW) ; TUNG; CHAO-NIEN; (Tu-Cheng, TW) ; LIU;
TAY-JIAN; (Tu-Cheng, TW) |
Correspondence
Address: |
PCE INDUSTRY, INC.;ATT. CHENG-JU CHIANG JEFFREY T. KNAPP
458 E. LAMBERT ROAD
FULLERTON
CA
92835
US
|
Assignee: |
FOXCONN TECHNOLOGY CO.,
LTD.
Tu-Cheng
TW
|
Family ID: |
38647238 |
Appl. No.: |
11/309569 |
Filed: |
August 24, 2006 |
Current U.S.
Class: |
165/104.26 ;
165/146 |
Current CPC
Class: |
F28D 15/046
20130101 |
Class at
Publication: |
165/104.26 ;
165/146 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2006 |
CN |
200610060511.8 |
Claims
1. A heat pipe comprising: a metal casing containing a working
fluid therein, the casing comprising an evaporating section at one
end and a condensing section at an opposite end thereof, and a
central section located between the evaporating section and the
condensing section; a capillary wick arranged on an inner wall of
the casing and comprising a first wick segment corresponding to the
evaporating section, a second wick segment corresponding to the
central section and a third wick segment corresponding to the
condensing section; and a vapor passage formed inside of the casing
and enclosed by the capillary wick; wherein the second wick segment
arranged at the central section of the casing is made of
non-metallic material.
2. The heat pipe of claim 1, wherein the non-metallic material is
an organic material.
3. The heat pipe of claim 1, wherein the non-metallic material is
one of plastics, resin, wood fiber and cotton.
4. The heat pipe of claim 1, wherein the first wick segment
arranged at the evaporating section is a sintered-type wick and the
third wick segment arranged at the condensing section is one of a
sintered-type wick and a mesh-type wick.
5. The heat pipe of claim 4, wherein a capillary pore size of the
first wick segment at the evaporating section is smaller than that
of the third wick segment at the condensing section.
6. The heat pipe of claim 1, wherein the first and third wick
segments arranged at the evaporating and condensing sections of the
casing are also made of non-metallic material.
7. The heat pipe of claim 1, further comprising a tube attached
with an inner surface of the second wick segment at the central
section of the casing.
8. The heat pipe of claim 6, wherein thicknesses of the second and
third wick segments from the central section to the condensing
section of the casing are gradually decreased and a diameter of the
vapor passage is gradually increased therealong.
9. The heat pipe of claim 6, wherein thicknesses of the second and
third wick segments corresponding to the central and condensing
sections of the casing are thinner than a thickness of the first
wick segment corresponding to the evaporating section of the
casing.
10. The heat pipe of claim 9, wherein the vapor passage
corresponding to the central and condensing sections of the casing
has a diameter which is larger than that corresponding to the
evaporating section of the casing.
11. The heat pipe of claim 10, wherein the thicknesses of the
second and third wick segments corresponding to the central and
condensing sections of the casing are uniform.
12. A heat pipe comprising: a metallic, tubular casing having an
evaporating section for receiving heat, a condensing section for
releasing the heat and an adiabatic section between the evaporating
and condensing sections; and a capillary wick arranged on an inner
wall of the casing; wherein at least a part of the capillary wick
corresponding to one of the evaporating, condensing and adiabatic
sections of the casing is made of non-metallic material.
13. The heat pipe of claim 12, wherein the part of the capillary
wick is correspondent to the adiabatic section of the casing.
14. The heat pipe of claim 12, wherein a whole the capillary wick
is made of non-metallic material.
15. The heat pipe of claim 14, wherein a tube is attached to an
inner face of the capillary wick at a portion thereof corresponding
to the adiabatic section.
16. The heat pipe of claim 14, wherein the capillary wick at the
adiabatic and condensing sections has a gradually decreased
thickness along a direction from the adiabatic section toward the
condensing section.
17. The heat pipe of claim 14, wherein the capillary wick at the
adiabatic and condensing sections has a thickness smaller than that
at the evaporating section.
18. The heat pipe of claim 12, wherein the non-metallic material is
chosen from one of plastics and resin.
19. The heat pipe of claim 12, wherein the non-metallic material is
chosen from one of wood fiber and cotton.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to a heat transfer
apparatus, and more particularly to a heat pipe having a capillary
wick made of non-metallic material.
DESCRIPTION OF RELATED ART
[0002] As a heat transfer apparatus, heat pipes can transfer heat
rapidly and therefore are widely used in various fields for heat
dissipation purposes. For example, in the electronics field, heat
pipes are commonly used to transfer heat from heat-generating
electronic components, such as central processing units (CPUs), to
heat dissipating devices, such as heat sinks. A heat pipe in
accordance with the related art generally includes a sealed casing
made of thermally conductive material with a working fluid
contained in the casing. The working fluid is employed to carry
heat from one end of the casing, typically called the "evaporating
section", to the other end of the casing, typically called the
"condensing section". Specifically, when the evaporating section of
a heat pipe is thermally attached to a heat-generating electronic
component, the working fluid receives heat from the electronic
component and evaporates. Then, the generated vapor moves towards
the condensing section of the heat pipe under the vapor pressure
gradient between the two sections. In the condensing section, the
vapor is condensed to liquid state by releasing its latent heat to,
for example, a heat sink attached to the condensing section. Thus,
the heat is removed from the electronic component.
[0003] In order to rapidly return the condensed liquid back from
the condensing section to the evaporating section to start another
cycling of evaporation and condensation, a capillary wick is
generally provided on an inner surface of the casing in order to
accelerate the return of the liquid. In particular, the liquid is
drawn back to the evaporating section by a capillary force
developed by the capillary wick. The capillary wick may be a
plurality of fine grooves defined in its lengthwise direction of
the casing, a fine-mesh wick, or a layer of sintered metal or
ceramic powders.
[0004] However, these capillary wicks are generally made of metal
material. These metallic-type capillary wicks generally cannot
provide a low cost and a lightweight advantage to the heat pipes.
Besides, the oxidation problem of the metal material may change
surface tension of the metallic-type capillary wick, whereby
quality of the heat pipes is difficult to control. Moreover,
porosity of the metallic-type capillary wick is limited during
manufacturing of the metallic-type capillary wick and, accordingly,
the heat transfer efficiency of the heat pipe cannot be enhanced to
a satisfied level.
[0005] In view of the above-mentioned disadvantage of the heat
pipe, there is a need for a heat pipe having good heat
transfer.
SUMMARY OF THE INVENTION
[0006] A heat pipe in accordance with a preferred embodiment of the
present invention includes a metal casing and a capillary wick
arranged on an inner surface of the casing. The casing has an
evaporating section, a condensing section and a central section
between the evaporating and condensing sections. The capillary wick
arranged at the central section is made of non-metallic material.
The capillary wick at the central section of the casing provides a
low cost and a lightweight to the heat pipe.
[0007] Other advantages and novel features of the present invention
will become more apparent from the following detailed description
of preferred embodiment when taken in conjunction with the
accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Many aspects of the present apparatus and method can be
better understood with reference to the following drawings. The
components in the drawings are not necessarily drawn to scale, the
emphasis instead being placed upon clearly illustrating the
principles of the present apparatus and method. Moreover, in the
drawings, like reference numerals designate corresponding parts
throughout the several views.
[0009] FIG. 1 is a longitudinal cross-sectional view of a heat pipe
in accordance with a first embodiment of the present invention;
[0010] FIG. 2 is a longitudinal cross-sectional view of a heat pipe
in accordance with a second embodiment of the present
invention;
[0011] FIG. 3 is a longitudinal cross-sectional view of a heat pipe
in accordance with a third embodiment of the present invention;
[0012] FIG. 4 is a longitudinal cross-sectional view of a heat pipe
in accordance with a fourth embodiment of the present invention;
and
[0013] FIG. 5 is a longitudinal cross-sectional view of a heat pipe
in accordance with a fifth embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] FIG. 1 illustrates a heat pipe in accordance with a first
embodiment of the present invention. The heat pipe comprises a
metallic casing 100 and a capillary wick 200 arranged on an inner
wall of the casing 100. A column-shaped vapor passage 300 is
enclosed by an inner surface of the capillary wick 200 in a center
of the casing 100. The casing 100 comprises an evaporating section
400 at one end, a condensing section 600 at an opposite end
thereof, and a central section (i.e., adiabatic section) 500
located between the evaporating section 400 and the condensing
section 600. The casing 100 is made of highly thermally conductive
materials such as copper or copper alloys and filled with a working
fluid (not shown) therein, which acts as a heat carrier for
carrying thermal energy from the evaporating section 400 to the
condensing section 600. Heat that needs to be dissipated is first
transferred to the evaporating section 400 of the casing 100 to
cause the working fluid therein to evaporate. Then, the heat is
carried by the working fluid in the form of vapor to the condensing
section 600 where the heat is released to ambient environment, thus
condensing the vapor into liquid. The condensed liquid is then
brought back via the capillary wick 200 to the evaporating section
400 where it is again available for evaporation.
[0015] The capillary wick 200 is a composite wick and comprises a
first wick segment 240 arranged at the evaporating section 400, a
second wick segment 250 located at the central section 500 which is
made by organic material with macromolecule and a third wick
segment 260 arranged at the condensing section 600. The first wick
segment 240 and the third wick segment 260 each are a sintered-type
wick or a mesh-type wick. The capillary pore size of the first wick
segment 240 is smaller than that of the third wick segment 260 and
the porosity of the first wick segment 240 is larger than that of
the third wick segment 260 so that the first wick segment 240 can
contain more working fluid than the third wick segment 260. The
second wick segment 250 is made of non-metallic material such as
plastics, resin or a combination of plastics and resin so as to
reduce weight of the heat pipe and enable the heat pipe to have a
low cost. The capillary pore size of the second wick segment 250
can be effectively controlled during manufacturing of the second
wick segment 250. The porosity of the second wick segment 250 can
be increased to increase the total porosity of the capillary wick
200. Since more working fluid can be received in the heat pipe in
accordance with the present invention, heat exchange between the
heat pipe and a heat-generating electronic component such as a CPU
can be improved and the heat transfer efficiency of the heat pipe
can be enhanced, accordingly.
[0016] In this embodiment, the capillary wick 200 has different
characteristics at different sections of the heat pipe. The third
wick segment 260 has a relatively larger capillary pore size and
therefore provides a relatively lower flow resistance to the
condensed liquid to flow therethrough, and meanwhile, the first
wick segment 240 has a relatively smaller average capillary pore
size and accordingly develops a relatively larger capillary force
to the liquid. As a result, the third wick segment 260 reduces the
flow resistance the condensed liquid encounters when flowing
through the condensing and central sections 600, 500, and the first
wick segment 240 has a large capillary force and therefore the
liquid is then rapidly drawn back to the evaporating section 400
from the central section 500 as the liquid reaches to a position
adjacent to the evaporating section 400. The condensed liquid is
returned back from the condensing section 600 in an accelerated
manner. After the condensed liquid is returned back to the
evaporating section 400, another phase-change cycle of the working
fluid will then begin. Thus, as a whole, the thermal transfer cycle
of the working fluid is accelerated and therefore the total heat
transfer capacity of the heat pipe is enhanced. Alternatively,
other organic material, such as wood fiber or cotton is feasible to
make the second wick segment 250.
[0017] FIG. 2 illustrates a heat pipe in accordance with a second
embodiment of the present invention. Main differences between the
first and second embodiments are that a whole of the capillary wick
210 in the second embodiment is made of non-metallic material. As a
result, the heat pipe can be very light. Additionally, formation of
the capillary wick 210 does not require a high temperature process
such as sintering; thus, oxidation of the metal casing can be
avoided. The other structure of the heat pipe of the second
embodiment is similar to that of the first embodiment.
[0018] FIG. 3 illustrates a heat pipe in accordance with a third
embodiment of the present invention. Main differences between the
third and second embodiments are that in the third embodiment a
tube 700 is attached with an inner surface of the capillary wick
210 at the central section 510 of the casing 110. The vapor passage
310 is separated from the capillary wick 210 by the tube 700.
Because of an arrangement of the tube 700 attached on the capillary
wick 210 at the central section 510 of the casing 110, the vapor
flows only along the vapor passage 310 toward the condensing
section 610 and the liquid flows only in the capillary wick 210
towards the evaporating section 410 when they flow in the central
section 510. The vapor and the liquid in the central section 510
are separated by the tube 700, which can avoid the adverse contact
between the vapor and liquid, wherein the vapor and the liquid flow
in opposite directions. Thus, the condensed working fluid from the
condensing section 610 can smoothly reach the evaporating section
410 and is prevented from being heated by the high temperature
vapor at the central section 510. Abilities of heat-absorption and
heat-dissipation of the working fluid of the heat pipe is further
enhanced and heat-transfer efficiency of the heat pipe is
accordingly further improved.
[0019] FIG. 4 illustrates a heat pipe in accordance with a fourth
embodiment of the present invention. Main differences between the
fourth and second embodiments are that in the fourth embodiment a
thickness of the capillary wick 220 from the central section 520 to
the condensing section 620 of the casing 120 is gradually decreased
along a longitudinal direction of the casing 120 and the vapor
passage 320 enclosed by the capillary wick 220 corresponding to the
central section 520 and the condensing section 620, is gradually
increased in the longitudinal direction of the casing 120. The
thinnest part of the capillary wick 220 is at the condensing
section 620 of the casing 120 so as to provide a low flow
resistance for the condensed liquid. The working fluid in vapor at
the condensing section 620 is quickly condensed and enters the
capillary wick 220. The thickness of the capillary wick 220 at the
evaporating section 420 is uniform. The capillary wick 220 at the
evaporating section 420 provides a large capillary wick force and
absorbs more of the working fluid at the evaporating section
420.
[0020] FIG. 5 illustrates a heat pipe in accordance with a fifth
embodiment of the present invention. Main differences between the
fifth and fourth embodiments are that in the fifth embodiment a
thickness of the capillary wick 230 at the central and condensing
sections 530, 630 of the casing 130 is uniform and thinner than
that at the evaporating section 430 of the casing 130. The
thickness of the capillary wick 230 at the evaporating section 430
is also uniform. The vapor passage 330 enclosed by the capillary
wick 230 at the central section 530 and the condensing section 630
has a diameter which is larger than that at the evaporating section
430.
[0021] It is to be understood, however, that even though numerous
characteristics and advantages of the present invention have been
set forth in the foregoing description, together with details of
the structure and function of the invention, the disclosure is
illustrative only, and changes may be made in detail, especially in
matters of shape, size, and arrangement of parts within the
principles of the invention to the full extent indicated by the
broad general meaning of the terms in which the appended claims are
expressed.
* * * * *